One popular understanding of John the Baptist’s time in the wilderness is that, though the text says he ate “locusts and wild honey,” he actually ate locust bean pods, not insects. This has become such a part of Christian mythology that the carob tree, which produces edible bean pods and is native to the Middle East, is also known as St. John’s Bread.
We find the description of John the Baptist’s diet in Matthew 3.4 and Mark 1.6. Both gospels say that he lived on ἀκρίδες καὶ μέλι ἄγριον — that is, locusts and wild honey. The key word here is ἀκρίς, meaning locusts. Besides these two verses, ἀκρίς also occurs in Revelation 9.3 and Revelation 9.7 where it is used to describe a plague of insects. Locusts are also listed in Leviticus 11.22 as one of the “clean” foods that are permissible to eat.
So is there any reason to think that ἀκρίς might refer to something other than flying insects? Of this notion, BDAG says “the widespread notion that the ἀ. were carob pods is supported neither by good linguistic evidence nor by probability.” Louw and Nida concur, saying
Some persons have assumed that the reference to grasshoppers being eaten by John the Baptist should be understood not as the insects but as carob pods, but there is neither linguistic nor cultural evidence to support such an interpretation. In a number of parts of the world there are different kinds of grasshoppers/locusts, some of which are edible, and others which are not edible. It is therefore important in the contexts of Mt 3.4 and Mk 1.6 to select a term which designates edible insects.
Interestingly, carob pods do make an appearance in the parable of the prodigal son (Luke 15.16). There, the text says “He longed to fill his stomach with the pods that the pigs were eating, but no one gave him anything.” The pods in questions are κεράτιον, defined by L&N as
the pod of the carob tree…Carob pods were commonly used for fattening swine and were employed as an article of food by poor people. In translating Lk 15.16 it is not necessary, however, to identify specifically carob pods. In most languages some such expression as ‘edible pods’ is probably more satisfactory, since carob trees are unlikely to be known.
So, it seems that there is no good basis to believe that John the Baptist subsisted on anything other than insects and honey. R.T. France, in the New International Commentary on Matthew sums things up nicely:
There is no basis in Greek usage for the strange notion, still sometimes encountered, that ἀκρίδες refers here not to locusts but to the carob or “locust” bean (so called because its pods resemble locusts), which thus came to be known as “St. John’s bread.” This idea derives from Western squeamishness rather than from the realities of Middle Eastern diet. John was an ascetic, but not a vegetarian!